The invention relates to devices and methods for installing rivets or other fasteners through workpieces such as wing skins, fuselage skins, or the like. The invention more particularly relates to automated devices and methods for drilling holes through a workpiece and installing fasteners into the holes.
Installation of rivets or other types of fasteners in large airframe structures such as wing skins, fuselage skins, and the like, is typically performed either manually or by large computer-controlled machines. The manual process involves two workers disposed on opposite sides of the workpiece to be fastened. The workers install clamping devices, for example by drilling holes through the workpiece and installing temporary fasteners and/or clekos into the holes, so as to clamp together the parts to be joined. Next, a hole is drilled through the workpiece with a hand-held drill, a rivet is installed into the hole, and the two workers use an impact hammer on one side of the workpiece and an anvil on the other side to upset the rivet.
The manual process is time consuming and expensive, but has been necessary in situations where an automated machine cannot access the workpiece. For example, in fuselage barrels, it has not been possible to install rivets with existing automated machines, because there is no way for the machine to simultaneously access both sides of a fuselage skin. Most automated machines employ some version of a C-frame device, in which the workpiece to be operated upon must be capable of being disposed between the two opposing jaws of the C-frame. The C-frame jaws support tooling such as drills and riveters. A riveter generally requires two cooperative tooling elements, one located on one of the jaws of the C-frame and the other located on the other jaw, so that the two tooling elements can be disposed on opposite sides of a workpiece. A C-frame riveter may also include cooperative clamping elements for clamping the workpiece between the jaws. For small structures, where the distance from an edge of the structure to the location at which a rivet is to be installed is less than the length of the jaws, a C-frame riveter can be used. However, for areas that cannot be accessed by the jaws of a C-frame riveter, such as inside wings and fuselage barrels, an alternative approach is needed. Preferably, the alternative approach should use automation at least to some extent, so that the time and expense of installing rivets can be reduced relative to manual riveting.
The above needs are met and other advantages are achieved by the present invention, which provides an apparatus for installing rivets or other fasteners through a workpiece combining an automated machine disposed on one side of the workpiece and a hand-held tool that is manipulated by a single worker located on the opposite side of the workpiece. The automated machine includes an end effector supporting tools such as a drill for drilling a hole through a workpiece, and a riveter for installing a rivet into the hole. The automated machine also includes a guide structure, such as a pair of guide rails, adapted to be releasably affixed to or adjacent to the workpiece, and a carriage that travels along the guide structure and supports the end effector so that the end effector can be positioned in a desired location along the surface of the workpiece where a fastener is to be installed. The end effector includes an electromagnetic clamping device that generates a magnetic field. The end effector also includes a positioning device that generates a positioning signal detectable on the opposite side of the workpiece.
The hand-held tool includes a magnetic clamping block, such as a steel block or the like. When the magnetic clamping block is placed against the opposite surface of the workpiece on the side opposite from the end effector, the magnetic field of the clamping device will cause the clamping block to be attracted toward the clamping device, thus clamping the workpiece therebetween. The hand-held tool includes a detector for detecting the positioning signal of the positioning device. The detector is operable to generate guidance information telling the person operating the hand-held tool where to move the hand-held tool so as to align the tool with the end effector of the automated machine. The hand-held tool may include a visual display, such as a liquid crystal display or light-emitting diode display, for displaying the guidance information in graphical or other form. Once the hand-held tool is aligned with the end effector, the electromagnetic clamping device is activated to clamp the workpiece, and then the end effector tools are operated to drill a hole and to install a rivet or other fastener into the hole.
Preferably, the hand-held tool includes a command signal generator operable to generate a command signal, and the end effector is operable to receive the command signal and to activate the electromagnetic clamping device upon receipt of the command signal. Thus, for example, once the hand-held tool is aligned with the end effector, the operator may pull a trigger or operate some other switch device on the hand-held tool so as to generate the command signal telling the end effector to begin the clamping and other operations.
In accordance with a preferred embodiment of the invention, the positioning device on the end effector comprises the electromagnetic clamping device itself Advantageously, the clamping device can generate a relatively weak magnetic field for positioning purposes, enabling the detector on the hand-held tool to detect this field and generate the guidance information telling the worker how to align the tool with the end effector. The detector may comprise, for instance, a magnetic compass or similar type of sensor. Once the tool is aligned, the worker activates the command signal generator. The end effector receives the command signal, which causes the current supplied to the electromagnetic clamping device to be increased for clamping the workpiece.
Where the end effector includes a riveter for installing a rivet into the hole drilled by the automated machine, the hand-held tool advantageously is operable to facilitate upsetting the rivet, for example through passive bucking (i.e., anvil upsetting). Alternatively, the end effector may be operable to install another type of fastener, for example a lock bolt or the like, that does not require cooperation by the hand-held tool, in which case the hand-held tool performs primarily a clamping function in cooperation with the automated machine.
After completion of the installation of a fastener, the end effector advantageously is operable to signal the worker that the operation is completed. The worker may then deactivate the hand-held tool, for example by releasing a trigger or the like, so that the hand-held tool in turn causes the electromagnetic clamping device to be deactivated. The clamping force is thus removed, and the automated machine can be moved to a new location for a subsequent fastener installation to be performed. Alternatively, the end effector may automatically deactivate the electromagnetic clamping device once installation of the fastener is complete, so that no action of the worker is required to release the clamping force on the workpiece.
The invention thus enables fasteners to be installed in workpieces in situations where a C-frame machine or the like would not be usable, and at the same time avoids the need for two workers as required with the conventional manual process. The apparatus and method of the invention also enable improved accuracy in fastener location and installation relative to the manual process. The method of fastener installation in accordance with the invention is also faster than the conventional manual process.